LS 500 Suspension moving on stopping
 

I have a 2018 LS 500 with 24000 Miles. I identified an issue with the suspension about 3 years ago that has not been correct. When I approach a stop at low speed and apply my breaks the suspension feels like moves back and forth. The sound is like something sliding back and forth in the trunk. To date Lexus has not been able to address the problem although I recently took the car in for service and had the service manager take a drive with me. He did hear and feel the suspension ? moving upon stopping. He then made an interesting comment that I had not hear before. He said that This is common with some 2018 LS models and is regarded as normal. This response is unacceptable. I have had there Lexus vehicles in addition to many other high end cars and there has never been this suspension shift ? when you stop. Has anyone had this issue? Is there any kind of Lexus repair letter that has address the issue.
Thank You